Causes of mortality in northern elephant seal pups on San Miguel Island, California

In February 2015, we conducted a field study of causes of mortality of northern elephant seal ( Mirounga angustirostris) pups on San Miguel Island, California. Autopsies were performed on 18 freshly dead pups. Ages of pups ranged from stillborn to 6–8 wk. Gross and histologic lesions included trauma (9 of 18 pups), multifocal necrotizing myopathy (8 of 18), starvation with emaciation (7 of 18), congenital anomalies (3 of 18), bacterial infections (3 of 18), and perinatal mortality (stillbirths and neonates; 2 of 18). Trauma and emaciation or starvation were the most significant contributors to death. Bacterial infections included hemolytic Escherichia coli isolated from the lungs of 2 pups with pneumonia. Additionally, non-hemolytic Streptococcus sp. and hemolytic E. coli were isolated from the liver of an emaciated pup that had mild multifocal suppurative hepatitis. Other lesions, including a previously described necrotizing myopathy, congenital anomalies, and bacterial infections, were detected concurrently in cases with starvation and/or emaciation or trauma.

Download Full-text

Multifocal Necrotizing Myopathy in Northern Elephant Seal (Mirounga angustirostris) Pups, San Miguel Island, California

Veterinary Pathology ◽

10.1177/0300985818790268 ◽

2018 ◽

Vol 56 (1) ◽

pp. 143-151 ◽

Cited By ~ 1

Author(s):

Terry R. Spraker ◽

Tetiana A. Kuzmina ◽

Eugene T. Lyons ◽

Robert L. DeLong ◽

Claire Simeone ◽

...

Keyword(s):

Elephant Seal ◽

Mirounga Angustirostris ◽

Northern Elephant Seal ◽

Vacuolar Degeneration ◽

Necrotizing Myopathy ◽

Eosinophilic Cytoplasm ◽

Northern Elephant Seals ◽

San Miguel Island ◽

System Degeneration ◽

Causes Of Mortality

A field study addressing causes of mortality in freshly dead northern elephant seals ( Mirounga angustirostris, Gill, 1866) was conducted on San Miguel Island, California, in February 2015. Necropsies were performed on 18 pups ranging in age from stillbirths to approximately 7 to 8 weeks. The primary gross diagnoses in these pups included trauma, myopathy, starvation/emaciation, infections, congenital anomalies, and perinatal mortality. However, 6 (33%) had a previously unrecognized myopathy characterized by multiple white streaks that were most obvious within the inner layer of the abdominal wall and the small innermost ventral intercostal muscles. Following histological examination, 2 more pups from San Miguel Island and 6 pups from The Marine Mammal Center (Sausalito, California) were found to have similar lesions. Histologically, the lesions within the skeletal muscles were characterized by a multifocal polyphasic, mild to severe, acute to subacute necrotizing myopathy with mineralization. Acute necrosis and degeneration characterized by pyknotic nuclei, eosinophilic cytoplasm and cytoplasmic vacuolization were found in smooth muscle myocytes within the urinary bladder and digestive system. Degeneration of myocytes was present in the tunica media of a few small- to medium-sized vessels and was characterized by a vacuolar degeneration and occasionally necrosis. This condition has been termed multifocal necrotizing myopathy. A cause of this myopathy was not identified.

Download Full-text

Parasitological examination of northern elephant seal (Mirounga angustirostris) pups for presence of hookworms (Uncinaria spp.) on San Miguel Island, California

Helminthologia ◽

10.1515/helmin-2016-0009 ◽

2016 ◽

Vol 53 (2) ◽

pp. 191-194

Author(s):

E. T. Lyons ◽

T. A. Kuzmina ◽

T. R. Spraker ◽

R. L. Delong

Keyword(s):

Elephant Seal ◽

Mirounga Angustirostris ◽

California Sea Lions ◽

Northern Elephant Seal ◽

Parasitological Examination ◽

Sea Lions ◽

Fur Seals ◽

Third Stage ◽

Northern Fur Seals ◽

San Miguel Island

SummaryNecropsy and extensive parasitological examination of dead northern elephant seal (NES) pups was done on San Miguel Island, California, in February, 2015. The main interest in the current study was to determine if hookworms were present in NESs on San Miguel Island where two hookworm species of the genus Uncinaria are known to be present - Uncinaria lyonsi in California sea lions and Uncinaria lucasi in northern fur seals. Hookworms were not detected in any of the NESs examined: stomachs or intestines of 16 pups, blubber of 13 pups and blubber of one bull. The results obtained in the present study of NESs on San Miguel Island plus similar finding on Año Nuevo State Reserve and The Marine Mammal Center provide strong indication that NES are not appropriate hosts for Uncinaria spp. Hookworm free-living third stage larvae, developed from eggs of California sea lions and northern fur seals, were recovered from sand. It seems that at this time, further search for hookworms in NESs would be nonproductive.

Download Full-text

In-air hearing in Hawaiian monk seals: implications for understanding the auditory biology of Monachinae seals

Journal of Comparative Physiology A ◽

10.1007/s00359-021-01498-y ◽

2021 ◽

Author(s):

Brandi Ruscher ◽

Jillian M. Sills ◽

Beau P. Richter ◽

Colleen Reichmuth

Keyword(s):

Marine Mammals ◽

Elephant Seal ◽

Critical Ratio ◽

Mirounga Angustirostris ◽

Northern Elephant Seal ◽

Hearing Ability ◽

Highly Sensitive ◽

Monk Seals ◽

Management And Conservation ◽

Hearing Abilities

AbstractThe auditory biology of Monachinae seals is poorly understood. Limited audiometric data and certain anatomical features suggest that these seals may have reduced sensitivity to airborne sounds compared to related species. Here, we describe the in-air hearing abilities of a Hawaiian monk seal (Neomonachus schauinslandi) trained to participate in a psychophysical paradigm. We report absolute (unmasked) thresholds for narrowband signals measured in quiet conditions across the range of hearing and masked thresholds measured in the presence of octave-band noise at two frequencies. The behavioral audiogram indicates a functional hearing range from 0.1 to 33 kHz and poor sensitivity, with detection thresholds above 40 dB re 20 µPa. Critical ratio measurements are elevated compared to those of other seals. The apparently reduced terrestrial hearing ability of this individual—considered with available auditory data for a northern elephant seal (Mirounga angustirostris)—suggests that hearing in Monachinae seals differs from that of the highly sensitive Phocinae seals. Exploration of phylogenetic relationships and anatomical traits support this claim. This work advances understanding of the evolution of hearing in amphibious marine mammals and provides updated information that can be used for management and conservation of endangered Hawaiian monk seals.

Download Full-text